1. Technical Field
The present disclosure relates to an image display device, and more specifically to an image display device suitable for being mounted in a vehicle or other movable body, for example.
2. Description of the Related Art
In recent years, image display devices called head-up displays to be mounted in vehicles or other movable bodies have been developed. When a head-up display is mounted in a vehicle, for example, the head-up display modulates light based on image information and irradiates a windshield with the modulated light. Then, the light is reflected by the windshield and incident on the driver's eyes. This enables the driver to see a virtual image based on the image information in front of the windshield. For example, a vehicle speed or an ambient temperature can be displayed as a virtual image. Studies are currently being conducted to display, as virtual images, a navigation image and an image for calling driver's attention to passengers, for example.
Some head-up displays, as described above, are equipped with a laser light source including a semiconductor laser, as their light source. This configuration scans a screen with a laser light beam modulated with a video signal. Then, the laser light beam is diffused by the screen whereby the driver's eyes are irradiated with the light incident from a wider area. This prevents the driver's eye from leaving the irradiated area even if he or she moves the head to some degree. Consequently, the driver can see the image (virtual image) appropriately and stably.
The head-up display configured as above moves the screen in parallel to a travel direction of the laser light beam, thereby displaying an image that has a depth. Unexamined Japanese Patent Publication No. 2009-150947 describes a configuration in which a screen moves in parallel to a travel direction of a laser light beam.